The successful knockout of Muc5ac has been achieved and was verified by genomic Southern, PCR and Muc5ac immunohistochemistry of various organs including the gastric stomach being determined. One major observation has been that the nasopharynx and conjunctiva of the Muc5ac-/- mice have significantly fewer and smaller goblet cells which contain decreased amount of mucous. Further studies of the nasopharynx of wild type and Muc5ac-/- mice have indicated mild to moderate hypertrophy and hyperplasia of the nasal lamina propria, epithelial hyperplasia and mid-septum and lateral wall of the Muc5ac-/- mice. Following respiratory syncytial virus (RSV) administration, more extensive congestion and edema was observed throughout the nasal cavity of the Muc5ac-/- mice. Furthermore, RSV-induced intraepithelial mucus secretion was significantly lower in the -/- mice. In summary to date, the pathological responses of the -/- mice to RSV were more extreme then observed in wild type mice. These studies are continuing with RSV time course experiments and various physiological consequences being determined. In addition, the pathological consequences of ozone exposure on wild type and Muc5ac-/- mice will be compared.